DE3831327A1 - METHOD FOR PRODUCING 1,1,2-TRIALCOXYETHANES - Google Patents

Description

The present invention relates to an improved method of manufacture of 1,1,2-trialkoxyethanes by reacting formaldehyde dialkyl acetals or of compounds under the reaction conditions Formaldehyde dialkyl acetals can form with carbon monoxide, hydrogen and alkanols in the presence of a catalyst consisting of a Cobalt carbonyl compound and a promoter.

From DE-A-36 27 776 it is known that trialkoxyethanes from formaldehyde acetals, Carbon monoxide, hydrogen and alkanols are produced if a cobalt carbonyl catalyst with a phosphine, arsine, Stibine or bismuth promoter is used. Disadvantages of this procedure are the relatively high price of the promoters used and others whose sensitivity to atmospheric oxygen.

From US-A-24 49 470 it is known that 1,1,2-trialkoxyethanes in the reaction of formaldehyde dialkyl acetals with carbon monoxide and hydrogen in the presence of an alkanol and a suspended cobalt oxide catalyst be preserved. The required reaction pressure is at least 600 bar.

DE-A-8 90 945 describes 1,1,2-trimethoxyethane and Ethylene glycol monomethyl ether from formaldehyde dialkyl acetal and one Carbon monoxide-hydrogen mixture known under increased pressure. As Catalyst is given cobalt oxide on silica gel. The selectivity for Trimethoxyethane leaves something to be desired.

The invention was based on the object of a method for the production Finding of 1,1,2-trialkoxyethanes, which has the aforementioned disadvantages remedies.

Accordingly, an improved process for the preparation of 1,1,2-trialkoxyethanes of the general formula I

in which R¹ to R³ independently of one another are C₁- to C₂₀-alkyl or cycloalkyl mean, or the radicals R¹ and R² together to form a 5- to 7-membered ring can be linked by reaction of Formaldehyde dialkyl acetals of the general formula II

in which R¹ and R² have the meanings given above, or of compounds which can formaldehyde dialkyl acetals under the reaction conditions, with carbon monoxide, hydrogen and alkanols R³OH at elevated pressure and elevated temperature in the presence of a catalyst consisting of a cobalt carbonyl compound and a promoter found, which is characterized in that the promoter is an alkali, alkaline earth or ammonium salt of a proton-active compound with an acid constant K _s of 10 ^-2 to 10 ^-14 or an alkali or alkaline earth metal hydroxide or an aminocarboxylic acid.

Serve as starting compounds for the process according to the invention Formaldehyde dialkyl acetals of the formula II

in which the radicals R¹ and R² are identical or different C₁- to C₂₀-alkyl- or cycloalkyl radicals or together to form a 5- to 7-membered ring are linked. Preferably R1 and R2 are primary or secondary C₁ to C₈ alkyl radicals, especially for primary C₁ to C₄ alkyl radicals. C₄- bis are suitable as cycloalkyl radicals C₁₂ cycloalkyl, preferably C₄ to C₈ cycloalkyl, especially C₅ to C₈-cycloalkyl.

R¹ and R² are, for example, methyl, ethyl, propyl, isopropyl, Butyl, isobutyl, pentyl, hexyl, heptyl, octyl, 2-ethylhexyl, cyclopentyl, Cyclohexyl and Cyclooctyl called. Cyclic acetals are e.g. B. 1,3-dioxolane or 1,3-dioxane. Instead of Acetale II, its precursors, namely formaldehyde or compounds operating under the reaction conditions Release formaldehyde, such as paraformaldehyde or trioxane, and the corresponding alcohols are used, the ratio of Aldehyde to alcohol can fluctuate within wide limits. Conveniently 1 to 5 moles of alcohol will be used per mole of aldehyde. Especially  acetals are preferably implemented, the alcohol component of which for Implementation used alcohol correspond to R³OH.

The alcohols R³OH are C₁ to C₂₀ alcohols, preferably C₁ to C₈ alcohols, especially C₁ to C₄ alcohols. For example the following alcohols are listed: methanol, ethanol, propanol, isopropanol, n-butanol, iso-butanol, n-pentanol, isoamyl alcohol, neopentyl alcohol, n-hexanol, hexanol-2, cyclohexanol, n-heptanol and n-octanol.

The formaldehyde dialkyl acetal II is used with at least equimolar amounts Alcohol R³OH implemented. The alcohol can advantageously be used in excess, e.g. B. 1 to 5, preferably 1.1 to 4, in particular 1.5 to 2.5 mol Alcohol R³OH per mole of acetal. Higher surpluses are possible, but bring no other advantages.

A carbon monoxide-hydrogen mixture is used for the hydroformylation of acetals II used, in particular 0.5 to 1.5 mol per mole of carbon monoxide 0.5 to 1 mol of hydrogen are present. The molar ratio is preferably CO: H₂ at 1: 1.

The process according to the invention is carried out in the presence of a catalyst which consists of a cobalt carbonyl compound and a promoter, the promoter being an alkali metal, alkaline earth metal or ammonium salt of a proton-active compound with an acid constant K _s of 10 ^-2 to 10 ^-14 or a Alkali or alkaline earth metal hydroxide or an amino carboxylic acid.

As cobalt carbonyl compound such. B. dicobaltoctacarbonyl or tetracarbonylhydridocobalt serve. The cobalt carbonyl compounds can also in situ from cobalt compounds, the cobalt carbonyl complexes under the reaction conditions can form, such as cobalt salts organic or inorganic Acids, e.g. B. cobalt acetate, cobalt laurate, cobalt 2-ethylhexanoate, Cobalt carbonate, cobalt nitrate or cobalt halides, or from Cobalt oxide can be produced.

Alkali, alkaline earth or ammonium salts can be used as promoters, such as B. Na₂HPO₄, Na₃PO₄, K₂HPO₄, K₃PO₄, KNH₄HPO₄, lithium acetate, Sodium acetate, potassium acetate, magnesium acetate, sodium propionate, sodium butyrate, Sodium 2-ethylhexanoate, ammonium acetate or sodium phenolate or Alkali or alkaline earth metal hydroxides, such as. B. lithium hydroxide, sodium hydroxide, Potassium hydroxide or calcium hydroxide, or aminocarboxylic acids such as Amino acetic acid, 2-aminopropionic acid, 3-aminopropionic acid or 2-aminobutyric acid. Preferably such compounds are used as promoters which are soluble in the reaction mixture, e.g. B. the salts of carboxylic acids,  such as lithium acetate, sodium acetate, potassium acetate, magnesium acetate, Potassium 2-ethylhexanoate, sodium stearate or potassium stearate. In particular such promoters are used as promoters in addition to the above properties must be available inexpensively, such as e.g. As sodium acetate, sodium propionate, sodium 2-ethylhexanoate or Amino acetic acid.

The catalyst is advantageously in situ from the cobalt carbonyl compound or its precursors and the promoter. The molar ratio The cobalt promoter is generally 0.1 to 2, preferably 0.3 to 1.5.

The cobalt concentration can be between 0.01 and 6% by weight, based on the Reaction mixture can be selected. Lower or higher concentrations are also possible.

The process according to the invention can be carried out in the presence or in the absence of Solvents. As a solvent such. B. ethers such as diethyl or diphenyl ether, aromatic or aliphatic hydrocarbons such as Benzene, toluene or hexane and alcohols. The serve advantageously alcohols R³OH required as a solvent for the reaction.

The reaction can be carried out batchwise or preferably continuously a pressure of 100 to 700, in particular 200 to 400 bar and a temperature from 50 to 300, preferably 100 to 250 ° C according to the usual Techniques are performed.

Then the trialkoxyethanes I in a conventional manner, for. B. be isolated from the mixture by distillation.

1,1,2-trialkoxyethane is a versatile intermediate for organic syntheses. For example, by acetal cleavage Alkoxyacetaldehyde are produced by condensation with Formaldehyde can be converted to polyols. By eliminating Alcohol can further dialkoxyethene, e.g. B. Dimethoxyethen prepared be used as a starting material for polymers.

Examples Examples 1 to 7

0.85 mol of methylal and 1.7 mol of methanol were introduced into an autoclave Presence of the catalyst consisting of dicobalt octacarbonyl and  Promoter, hydroformylated within 90 minutes at 150 ° C and 280 bar, the ratio of carbon monoxide to hydrogen was 1: 1. After cooling to room temperature and relaxing the autoclave Reaction discharge weighed and analyzed by gas chromatography. The attempts are summarized in Table 1.

Table 1

Hydroformylation of methylal

Examples 8 to 16

Analogously to Examples 1 to 7, 0.4 mol of butylal and 0.8 mol of butanol in the presence of 4 mmol dicobalt octacarbonyl and different promoters brought to reaction. The tests are summarized in Table 2.  

Table 2

Hydroformylation of butylal

Example 17

In a tube reactor with continuous flow from bottom to top a volume of 360 ml was 9800 g of a reaction solution containing 4870 g (64.1 mol) methylal, 4360 g (136.3 mol) methanol, 457.5 g (1.33 mol) cobalt-2-ethylhexanoate, 65.1 g (0.79 mol) sodium acetate an average reaction time of 30 minutes at 250 bar and 150 ° C hydroformylated. The solution initially contained 0.5% of the feed materials Water. The ratio of carbon monoxide to hydrogen was 1: 1. The relaxed one and cooled reaction discharge, 10 454 g, showed by gas chromatography Analysis of the following composition for: 3753 g (49.4 mol) Methylal, 3910 g (122.2 mol) methanol, 1516 g (12.6 mol) 1,1,2-trimethoxyethane, 314 g (17.4 mol) of water, 31.9 g (0.4 mol) of ethylene glycol monomethyl ether and 63 g (0.9 mol) methoxyacetaldehyde and unspecified Proportions of higher boiling components and the catalyst.

Claims (4)

1. Process for the preparation of 1,1,2-trialkoxyethanes of the general formula I in which R¹ to R³ independently of one another are C₁- to C₂₀-alkyl or cycloalkyl, or the radicals R¹ and R² can be linked together to form a 5- to 7-membered ring, by reacting formaldehyde dialkyl acetals of the general formula II in which R¹ and R² have the meanings given above, or of compounds which can formaldehyde dialkyl acetals under the reaction conditions, with carbon monoxide, hydrogen and alkanols R³OH at elevated pressure and elevated temperature in the presence of a catalyst consisting of a cobalt carbonyl compound and a promoter , characterized in that the promoter is an alkali, alkaline earth or ammonium salt of a proton-active compound with an acid constant K _s of 10 ^-2 to 10 ^-14 or an alkali or alkaline earth hydroxide or an amino carboxylic acid. 2. The method according to claim 1, characterized in that the promoter is an alkali, alkaline earth or ammonium salt of a carboxylic acid. 3. The method according to claim 1, characterized in that one per mol Cobalt 0.1 to 2 mol promoter used. 4. The method according to claim 1, characterized in that formaldehyde or compounds that formaldehyde under the reaction conditions release, and the appropriate alcohols used.